I have a dual zone Lennox system, and it cools well, but for the past few weeks it seems to run away at random cooling the upstairs to several degrees lower than requested.

We have EcoBee thermostats and have them set to AUTO with a range of 72 ( heat ) and 76 ( cool ) this will generally give us a temperature of 74 or 75. If anyone gets hot, and sets the temp a little lower like say 74 ( cool ), it will continue to cool until i reset the breaker on the system. ( last night the upstairs got to around 62 before i got home )

It seems like something is sticking, like a contact or something.

Any idea what could cause this ?

  • How are you measuring temperature: independent gauge or Ecobee room sensor measurements? (Do you have the remote sensors for the Ecobee?) If you do have the Ecobee room sensors, any chance that a remote sensor is configured as the only one to control temperature at night but not during the day and it is somewhere really hot and isolated from the upstairs or is malfunctioning (e.g. it still thinks its 76 for some reason wherever it is located when the upstairs is actually 62 as you stated)? – statueuphemism May 18 at 0:04

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